Reproductive biology of Calcinus laevimanus (Randall, 1840) (Decapoda: Anomura: Diogenidae) from Inhaca Island, southern Mozambique

Abstract

Hermit crabs are one of the most abundant taxa in the intertidal habitats of tropical estuarine areas. Despite this situation, many aspects concerning their population ecology and reproduction are still poorly known. In this study, the reproductive biology of the diogenid hermit crab, Calcinus laevimanus was studied with emphasis on size structure, sex ratio, recruitment, breeding season and fecundity. Monthly samplings were conducted between January and December 2003 at Inhaca Island, southern Mozambique. A total of 1966 crabs were collected, represented by 760 males and 1206 females. The size frequency distribution of the present population showed an unimodal pattern skewed to the right, suggesting increased mortality in the largest size classes. Sexual dimorphism was evidenced by the larger sizes attained by males in relation to females. Moreover, sex ratios were femalebiased during most of the study period. Juvenile recruitment was constant with major peaks in March and May, ovigerous females were present year-round peaking February and April and egg number increased with female size. The present results show that reproduction and recruitment of Calcinus laevimanus displays high reproductive activity in the study area, as evidenced by the constant presence of ovigerous females and the high number of eggs carried by females.